Process for producing a cellulose of high content of alpha cellulose



Patented July 24, 1934 OF HIGH CONTENT OF.

LOSE

ALPHA CELLU- Alions Bayerl, Dessau in Anhalt, Germany, assignor to I; G. Farbenlndustrie Aktiengeseilschait, Frankfort-on-the-Main, Germany No Drawing. Application October 3, 1933, Serial No. 692,038. 'In Germany October 8, 1932 6 Claims. (Cl. 92-9) My present invention relates to an improved method for producing an extremely pure-cellulose and provides a process which allows the manufacture of a cellulose of high content of a-cellulose in a very simple and cheap manner.

I have found that a very pure cellulose is formed when subjecting a pulp obtained by any opening-up process of cellulose to a chlorination process and then treating this product either 10 in the cold or at an elevated temperature with a caustic soda lye of to per cent strength while simultaneously introducing gaseous chlorine into the mixture.

In this last mentioned step the quantity of chlorine preferably is so measured that it is completely consumed during this bleaching operation. In the most cases the amount of chlorine does not surpass about 2 per cent calculated on the dry cellulose for obtaining the desired eflect. By this process it becomes possible to carry out the finishing of the cellulose at an elevated temperature as, for instance, about 60 C. in an essentially shorter time than usual without damaging the cellulose fibers. A final 2 separate bleaching of the pulp asusually done thus becomes unnecessary. The cellulose products thus obtainable in a very good yield, are distinguished by theirhigh content of a-cellulose; they show a very low copper number and have only a very small content of resin or fat.

This new improving process is applicable for all kinds of cellulose produced from beech, pine, fir and so on.

The following examples serve to illustrate our invention without limiting it to the specific details given therein.

Example 1.-A moist beech cellulose pulp obtaincd, for instance, according to the opening up process disclosed in U. 8. Patent No. 1,840,198.

2.5 per cent of chlorine calculated on the dry cellulose under treatment. Then, if desired, ai'tor washing the mass with a very diluted solution of caustic alkali for removing. the chlorinated lignine residues, a solution of caustic alkali is added,-so that a lye oi 9 per cent strength is formed, while simultaneously introducing rapidly gaseous chlorine in an amount of 2 per cent calculated on the dry cellulose: the temperature 5 being kept during this treatment at 60 C. for

1 to 2 hours.

Example 2.-A beech cellulose pulp obtained, for instance, in the same manner as indicated in Example 1, is treated at about C. with chlorine in an amount of about 3 per cent, calis treated at ordinary temperature with about,

culated on the quantity of dry cellulose under treatment, and then, the case given after washing with a very dilute alkali solution, a further treatment is followed with caustic alkalioi 9 per cent strength for 3 to 4 hours at about 25 to about 30" C.-, while simultaneously 1.5 per cent of gaseous chlorine, likewise calculated on the dry cellulose, is acted upon the mass.

By variating the concentration of the alkali, the temperature or duration of treatment, any desired viscosity of the cellulose is obtainable. The highly pure cellulose thus obtainable, can be used for all purposes, for instance, for manufacturing cellulose esters, nitro cellulose, artiflcial silk, and similar products.

What I claim is:-

1. The process for producing a cellulose of high content of a-cellulose which comprises treating an opened-up moist cellulose material with chlorine, then adding caustic alkali to form ,in the pulp a lye of 5 to 10 per cent strength while simultaneously introducing rapidly gaseous'chlorine into the mixture.

2. The process for producing a cellulose 01 high content of a-CCIIUIOSC which comprises treating an opened-up moist cellulose material with chlorine, washing the pulp with a highly diluted caustic alkali solution, then adding caustic alkali to form in the pulp a lye of 5 to 10 per cent strength while simultaneously introducing rapidly gaseous chlorine into the mixture.

3. The process for producing a cellulose of high content of a-OQllUlOSE which comprises treating an opened-up moist cellulose material with chlorine, washing the pulp with a highly diluted caustic alkali solution, then adding caustic alkali to form in the pulp a lye of 5 to 10 per cent strength while simultaneously introducing rapidly gaseous chlorine into the mixture in such an amount that the chlorine is completely consumed.

4. The process for producing a cellulose of high content of a-CClllllOSC which comprises treating an opened-up moist cellulose material with chlorine, then adding caustic alkali to form in the pulp a lye of 5 to 10 per cent strength while simul- 10o tancously introducing rapidly gaseous chlorine into the mixture in such an amount that the chlorine is completely consumed. and keeping the mass at a temperature oi about 30 to about C.

5. The process for producing a cellulose of high 105 content of -a-C(311ll10$(2 which comprises treating an opened-up moist cellulose material with chlorine, washing the pulp with a highly diluted caustic alkali solution, then adding caustic alkali to form in the pulp a lye of 5 to 10 per cent strength 110 calculated on the dry cellulose, washing the pulp with a highly diluted caustic alkali solution, then adding caustic alkali, so that a lye of 9 per cent strength is formed, introducing rapidly 1.5 to 2 per cent of chlorine andallowing the liquid to act upon the cellulose for about 1 to 4 hours at a temperature between 30 to C. A

ALFONB BAYERL. 

